1. Technical Field
The present invention is directed generally to electromechanical machines, and, in particular, to a system and a method for current regulation in the field-weakening operation of induction machines.
2. Description of the Related Art
In the control of inverter-driven induction machines, field weakening is often used to lower the inverter voltage rating for a given application. Without field weakening the inverter manufacturer would have to use components rated to handle higher levels of voltage for that given application. This would undesirably add incremental costs to the drive system. During high speed operation, the phase current may be applied to the machine windings in advance of the phase electromotive force. To control the electromotive force, the D axis current is decreased inversely with speed.
It is known to provide a flux weakening algorithm by the use of a number of look-up tables to produce the reference Q-axis and D-axis currents. However, the use of look-up tables requires the creation of numerous and cumbersome data structures within the look-up tables themselves to handle all possible situations in the system and its environment.
Accordingly, there is a need for a current control system that minimizes or eliminates one or more of thc above-mentioned shortcomings.